Steering wheel command and CarPC inteface for New Renault

Hi all,
This is my first post, I think to mount a carpc in my new car, a renault megane 2, I've original car hifi whit steering wheel that I want to inteface whit carpc.

I've found the manual of my car, I've read that there is a connector whit 7 cable, when I press a button I've 0,5 ohm from pin 1 and pin 4 for example.
Now the problem is to convert this resistor to a signal for serial, parallel or joystick port and make a plugin for carpc.

If there is anyone interested to this post and have any ideas to make the interface please contact me.